Method of producing a suspension of fibrous material



fieph m ww B G, WAHUN 241,959

METHOD OF PRODUCING A SUSPENSION OF FIBROUS MATERIAL Filed Dec. 21. 1945 2 Sheets-Sheet l Swt 113, WWW B. G. WAHLlN 9 3 METHOD OF PRODUCING A SUSPENSION OF FIBROUS MATERIAL Filed Dec. 21, 1945 2 Sheets-Sheet 2 Patented Sept. 13, 1949 METHOD OF PRODUCING A SUSPENSION OF FIBROUS MATERIAL Bengt Gustaf Wahlin, Kramfors, Sweden, as-

signor to Svenska Cellulosa Aktiebolaget,

Stockholm, Sweden Application December 21, 1945, Serial No. 636,488

In Sweden January 11, 1945 The present invention has for its object to obtain a foamy mass of a foaming agent, e. g.. sulphite residual liquor, and a fibrous material suspended in water, said foamy mass being particularly suitable for the manufacture of highly orous fibrous boards or similar products.

One object of the invention is to improve the methods hitherto used for the same purpose, according to which methods the foamy mass is produced in separate vessels provided with complicated and expensive stirring propellers or the like and corresponding driving means, said stirrers being destroyed rapidly on account of the permanent Wear.

The method according to the present invention chiefly consists therein that the fibrous suspension containing the foaming agent is' caused to pass through a conduit provided with a foaming section having air inlets and means for imparting a rotating or whirling motion to the suspension, while sucking in air through the air inlets so that the suspension when leaving the conduit has been transformed into a foamy mass.

In order to obtain a thorough agitation of the fibrous suspension, which is suitable for the homogeneity of the foamy mass the fibrous suspension together with the foaming agent and the sucked in air are preferably subjected to a repeated compression and expansion by being forced successively through constricted and expanded portions arranged alternatingly in the foaming section.

The invention also relates to an apparatus for carrying out the abovementioned method. Said apparatus comprises a supply pipe for the fibrous suspension and the foaming agent which pipe is provided with a foaming section havin one or .more preferably adjust-able members for imparting a whirling or rotary motion to the suspension when passing through the pipe. Further, the foaming section is provided with two or more constricted portions and with two or more expanded portions so that the suspension when passing through the foaming section will be compressed and expanded two times or more. At each constricted portion there is provided an air inlet so that air will be sucked in as the suspension leaves the compressed portions.

The accompanying drawings illustrate the invention diagrammatically.

Fig. 1 is a sectional view of the foaming section and Fig. 2 shows on a smaller scale an apparatus for carrying out the method according to the invention.

1 Claim. (Cl. 261-36) The fibrous suspension and the foaming agent are supplied through a conduit I which opens into a container 2. From the bottom of the container there emanates a conduit 3 provided with a pump 4 which sucks the liquid close to the bottom of the container 2 out through the conduit 3 and causes the same to pass through a foaming section (A in Fig. 2) provided in the conduit 3. This foaming section is shown on a larger scale in Fig. 1 and is provided with two air inlet conduits 5 having controlling valves 6 and with members I for imparting a whirling or rotary motion to the liquid passing through the foaming section. In the drawing two such members l are shown in the form of semicircular discs which are situated opposite each other in the conduit 3 and obliquely positioned in the opposite directions so that they form guiding members for the liquid. The conduit 3 is provided with a constricted portion 8 and opens into one end portion of a nozzle l U expanded relatively to the constricted portion 9 said nozzle l0 being constricted at its other end portion H and in its turn opening into the expanded end portion of another nozzle 12 formed in the same manner as the nozzle Ill. As will appear from Fig. 1 the air inlet conduits 5 are arranged at the constricted portions 9 and H.

The fibrous suspension and the foaming agent supplied through the conduit 3 are brought into a rotary motion when passing the members 1 so that the suspension after passing the compressed portion 9 will be thrown out against the inner circumference of the nozzle ill. Air is thereby sucked in through the adjacent conduit 5. When the liquid jet is then compressed in the narrower portion of the nozzle ill (the constricted portion ll) part of the entrained air is dissolved momentarily in the suspension on account of the increased pressure to reappear immediately in the form of small air bubbles when the jet is again extended when flowing into the nozzle I2. The jet being compressed and expanded two times when passing through the foaming section the fibrous material is subjected to an intense agitation, a great number of small air bubbles being now again obtained. The rotary motion im-' parted to the liquid by means of the members l.

is maintained in part during the passage through the nozzles Ill and I2. The formed foamy mass flows from the final nozzle l2 down into a foam container l3 in which an intense stirring treatment takes place only by the action of the jet from the nozzle [2. When the foamy mass in the container l3 has ascended to a certain height it overflows a wall ll into the container 2. The

foamy mass is discharged from the container II by means of a conduit I5.

The pump may work continuously independent of the discharges through the conduits I and 15. The rate of discharge through the conduit l5, however, ought to be less than the capacity of the pump.

The two member 1 imparting the rotary motion to the liquid may preferably be adjustable separately and may, while maintaining the intended function, be shaped in different ways so as to obtain a guiding action. For stirring the liquid a single damper-like member, which is adjustable by turning, may be used.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

Method of producing a stream of foamy suspension of fibrous material in an aqueous liquid containing a foaming agent, for use in forming highly porous fibrous boards and similar products, which comprises establishing a body of an aqueous suspension of fibers including a foaming agent, continuously withdrawing from adjacent the bottom of said body a stream of said suspension, imparting rotary as well as translational motion to said stream, subjecting the rotating stream to an intense agitation in the presence of air by repeatedly constricting said stream and 30 expandin the same in the presence of air, whereby air is introduced into said stream. jetting the resulting intensely agitated and foamy stream through air into said body of said suspension, continuously withdrawing foamy suspension from said body while the same is maintained in agitated foamy condition by said jetted stream, and continuously adding fresh aqueous suspension of fibers including a foaming agent to said body to maintain the latter.

BENGT GUSTAF WAHLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATEN'IS Number Name Date 1,995,540 Harrison Mar. 26, 1935 2,128,311 Mertes Aug. 30, 1938 2,183,561 Hamblin Dec. 19, 1939 2,324,605 Urquhart July 20, 1943 2,375,833 Urquhart May 15, 1945 FOREIGN PATENTS Number Country Date 441,441 Great Britain Jan. 20, 1936 467,359 Great Britain June 16, 1937 

